diff --git a/harnesses/gtauri/frontend/dist/index.html b/harnesses/gtauri/frontend/dist/index.html
index a6e97bd..eccc433 100644
--- a/harnesses/gtauri/frontend/dist/index.html
+++ b/harnesses/gtauri/frontend/dist/index.html
@@ -573,15 +573,29 @@ function commitTo(ni, delta) {
     if (t < 1) {
       tween = { raf: requestAnimationFrame(step), commit: true };
     } else {
-      // vimg2 (incoming) is exactly at 0: it becomes primary.
       const id = ids[ni];
-      vimg.src = vimg2.src; // cached + decoded → paints immediately
-      vTx = 0;
-      applyTransform();
       tween = null;
-      openViewer(id, true);
-      // Hide the outgoing preview only once the primary has the bytes.
-      vimg.onload = () => { if (viewerId === id) navHide(); };
+      if (nav && nav.id === id && nav.ready) {
+        // vimg2 (incoming) is exactly at 0: it becomes primary. Adopt
+        // its dimensions NOW — otherwise the new pixels render in the
+        // OLD image's width/height box (wrong aspect) until full-res
+        // lands and fitViewer() fixes it (visible stretch → snap).
+        const nw = nav.w, nh = nav.h, ns = nav.scale;
+        vimg.src = vimg2.src; // cached + decoded → paints immediately
+        base.w = nw; base.h = nh;
+        vScale = ns;
+        vimg.style.width = nw + "px";
+        vimg.style.height = nh + "px";
+        vTx = 0; vTy = 0;
+        applyTransform();
+        openViewer(id, true);
+        // Hide the preview only once the primary has the bytes.
+        vimg.onload = () => { if (viewerId === id) navHide(); };
+      } else {
+        // Preview never made it (keyboard nav / slow thumb): plain
+        // open — the thumb round-trip sets the right dimensions.
+        openViewer(id, false);
+      }
     }
   };
   tween = { raf: requestAnimationFrame(step), commit: true };